Selective cobalt removal for bottom up gapfill

ABSTRACT

Exemplary methods for removing cobalt material may include flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber. The methods may include forming a plasma of the chlorine-containing precursor to produce plasma effluents. The methods may also include contacting an exposed region of cobalt with the plasma effluents. The exposed region of cobalt may include an overhang of cobalt on a trench defined on a substrate. The plasma effluents may produce cobalt chloride at the overhang of cobalt. The methods may include flowing a nitrogen-containing precursor into the processing region of the semiconductor processing chamber. The methods may further include contacting the cobalt chloride with the nitrogen-containing precursor. The methods may also include recessing the overhang of cobalt.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/349,460, filed Nov. 11, 2016, and which is hereby incorporated byreference in its entirety for all purposes.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment.More specifically, the present technology relates to etching cobaltduring gapfill operations.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used inthe process. A wet HF etch preferentially removes silicon oxide overother dielectrics and materials. However, wet processes may havedifficulty penetrating some constrained trenches and also may sometimesdeform the remaining material. Dry etches produced in local plasmasformed within the substrate processing region can penetrate moreconstrained trenches and exhibit less deformation of delicate remainingstructures. However, local plasmas may damage the substrate through theproduction of electric arcs as they discharge.

Thus, there is a need for improved systems and methods that can be usedto produce high quality devices and structures. These and other needsare addressed by the present technology.

SUMMARY

Exemplary methods for removing cobalt material may include flowing achlorine-containing precursor into a processing region of asemiconductor processing chamber. The methods may include forming aplasma of the chlorine-containing precursor to produce plasma effluents.The methods may also include contacting an exposed region of cobalt withthe plasma effluents. The exposed region of cobalt may include anoverhang of cobalt on a trench defined on a substrate. The plasmaeffluents may produce cobalt chloride at the overhang of cobalt. Themethods may include flowing a nitrogen-containing precursor into theprocessing region of the semiconductor processing chamber. The methodsmay further include contacting the cobalt chloride with thenitrogen-containing precursor. The methods may also include recessingthe overhang of cobalt.

In exemplary methods a plasma power of the plasma formed from thechlorine-containing precursor may be less than about 100 W. Atemperature of the substrate may be maintained between about 175° C. andabout 250° C. during the etching method. A pressure within thesemiconductor processing chamber may be maintained below about 5 Torr inembodiments. The etching methods may remove at least about 5 Å of cobaltduring each removal or during the method operations. The methods mayalso include depositing additional cobalt in the trench, and producing asubsequent overhang. In some embodiments, the etching method may berepeated for at least two cycles. A total removal of cobalt after the atleast 2 cycles may be at least about 20 Å. In some embodiments themethod may further include, subsequent to recessing the overhang ofcobalt, contacting the substrate with effluents of a hydrogen-containingplasma, and removing residue from exposed cobalt surfaces. The methodsmay remove less than 5% of material proximate a bottom region of thetrench. The method may have a selectivity of cobalt to titanium nitridegreater than or about 50:1. The method may also have a selectivity ofcobalt to silicon nitride and silicon oxide greater than or about100:1:1. In some embodiments, the processing region may be maintainedplasma-free while contacting the cobalt chloride with thenitrogen-containing precursor.

The present technology may also include methods of producing a gap-freecobalt fill. The methods may include depositing a first amount of cobaltinto a trench defined on a substrate. The deposition may form anoverhang of cobalt at an opening of the trench. The methods may includeflowing a chlorine-containing precursor into a processing region of asemiconductor processing chamber. A substrate may be housed within theprocessing region. The methods may also include forming a plasma of thechlorine-containing precursor to produce plasma effluents. The methodsmay include contacting the overhang of cobalt with the plasma effluentsto produce cobalt chloride at the overhang of cobalt. The methods mayinclude flowing a nitrogen-containing precursor into the processingregion of the semiconductor processing chamber. The methods may furtherinclude contacting the cobalt chloride with the nitrogen-containingprecursor. The methods may include recessing the overhang of cobalt.

In some embodiments the methods may further include depositing a secondamount of cobalt into the trench. The deposition may form an additionaloverhang of cobalt at the opening of the trench. In some embodimentscertain operations of the methods or the entire methods may be repeatedat least twice. The first amount of cobalt may be at least 80%maintained in the trench while removing the overhang of cobalt. A plasmapower of the plasma formed from the chlorine-containing precursor may beless than or about 60 W. In some embodiments, the methods may furtherinclude, subsequent to recessing the overhang of cobalt, contacting thesubstrate with effluents of a hydrogen-containing plasma, and removingresidue from exposed cobalt surfaces. In some embodiments the cobalt maybe deposited on a metallic nitride liner formed within the trench.

Such technology may provide numerous benefits over conventional systemsand techniques. For example, the processes may remove an overhangportion of cobalt while substantially maintaining a portion of cobaltwithin the trench. Additionally, the removal operations of embodimentsof the present technology may run an all-in-one process in a singlechamber. These and other embodiments, along with many of theiradvantages and features, are described in more detail in conjunctionwith the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplaryprocessing system according to embodiments of the present technology.

FIG. 2A shows a schematic cross-sectional view of an exemplaryprocessing chamber according to embodiments of the present technology.

FIG. 2B shows a detailed view of a portion of the processing chamberillustrated in FIG. 2A according to embodiments of the presenttechnology.

FIG. 3 shows a bottom plan view of an exemplary showerhead according toembodiments of the present technology.

FIG. 4 shows exemplary operations in a method according to embodimentsof the present technology.

FIGS. 5A-5D show cross-sectional views of substrates being processedaccording to embodiments of the present technology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include exaggerated material forillustrative purposes.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a letter thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the letter.

DETAILED DESCRIPTION

As semiconductor device features continue to reduce in size, so do theinterconnects between the features. For feature sizes in much of thecurrent generation, copper interconnects have adequate resistivity,which may be less than cobalt. However, as features sizes continue todecrease below 20 nm, the effects may reverse, and cobalt may havereduced resistivity over copper. Tungsten is also a metal used in plugsand as a potential interconnect candidate. Similar to copper, though, asfeature sizes continue to reduce, the resistivity of tungsten may bemuch larger than for cobalt. A semiconductor chip less than a couplecentimeters in size may have dozens of miles of interconnect wiringrunning through the chip. Resistivity plays an important role insemiconductor performance, and the higher the resistivity, the morepower the device may draw. Accordingly, by utilizing lower resistivityconductors, power management may be better controlled.

Because of the high aspect ratios of vias and trenches, many depositiontechniques produce voids or keyholes when the top of a trench is sealedoff during the deposition. One technique for handling this issue is toperform a dep-etch-dep process, which may include intermediate processesin which a portion of the deposited material is removed in order toexpose the trench opening for better fill. Without complete fill,resistivity may increase, or the device may short circuit from thesevoids, which may render the device useless. Dep-etch-dep processes havebeen uncommon with cobalt because of the difficulty of cobalt removal.Many modified cobalt structures including cobalt fluoride, cobaltchloride, and cobalt bromide are non-volatile, and thus once formed maybe difficult to remove. Conventional technologies have been unable toprovide a cobalt etch with adequate queue times due to the multiplechambers, and multiple processes that may be used in an attempt to etchthe cobalt. Additionally, the etching techniques used may also removethe cobalt within the trench or feature, which may further extend theformation operations, and reduce the overall quality of the cobaltformed.

The present technology overcomes these issues by performing an etchprocess that preferentially removes a top region of cobalt whilemaintaining cobalt within the trench features. Additionally, the removaloperations may maintain a higher quality cobalt within the trench bothby limiting the etchant contact with the cobalt, and also with optionaloperations that clean the cobalt surface. Finally, the entire removalprocess may be performed in a single chamber, unlike wet etch techniquesthat require transferring the processed substrate between multiplechambers to perform the wet etch and then dry the substrate. Theseprocesses may allow the formation of a high-quality cobalt fill intrenches and other features, and may improve queue times overconventional technologies.

Although the remaining disclosure will routinely identify specificetching processes utilizing the disclosed technology, it will be readilyunderstood that the systems and methods are equally applicable todeposition and cleaning processes as may occur in the describedchambers. Accordingly, the technology should not be considered to be solimited as for use with etching processes or chambers alone. Moreover,although an exemplary chamber is described to provide foundation for thepresent technology, it is to be understood that the present technologycan be applied to virtually any semiconductor processing chamber thatmay allow the single-chamber operations described.

FIG. 1 shows a top plan view of one embodiment of a processing system100 of deposition, etching, baking, and curing chambers according toembodiments. In the figure, a pair of front opening unified pods (FOUPs)102 supply substrates of a variety of sizes that are received by roboticarms 104 and placed into a low pressure holding area 106 before beingplaced into one of the substrate processing chambers 108 a-f, positionedin tandem sections 109 a-c. A second robotic arm 110 may be used totransport the substrate wafers from the holding area 106 to thesubstrate processing chambers 108 a-f and back. Each substrateprocessing chamber 108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

The substrate processing chambers 108 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a dielectricor metallic film on the substrate wafer. In one configuration, two pairsof the processing chambers, e.g., 108 c-d and 108 e-f, may be used todeposit material on the substrate, and the third pair of processingchambers, e.g., 108 a-b, may be used to etch the deposited material. Inanother configuration, all three pairs of chambers, e.g., 108 a-f, maybe configured to etch a dielectric or metallic film on the substrate.Any one or more of the processes described may be carried out inchamber(s) separated from the fabrication system shown in differentembodiments. It will be appreciated that additional configurations ofdeposition, etching, annealing, and curing chambers for dielectric filmsare contemplated by system 100.

FIG. 2A shows a cross-sectional view of an exemplary process chambersystem 200 with partitioned plasma generation regions within theprocessing chamber. During film etching, e.g., titanium nitride,tantalum nitride, tungsten, copper, cobalt, silicon, polysilicon,silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide,etc., a process gas may be flowed into the first plasma region 215through a gas inlet assembly 205. A remote plasma system (RPS) 201 mayoptionally be included in the system, and may process a first gas whichthen travels through gas inlet assembly 205. The inlet assembly 205 mayinclude two or more distinct gas supply channels where the secondchannel (not shown) may bypass the RPS 201, if included.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225,and a substrate support 265, having a substrate 255 disposed thereon,are shown and may each be included according to embodiments. Thepedestal 265 may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate, whichmay be operated to heat and/or cool the substrate or wafer duringprocessing operations. The wafer support platter of the pedestal 265,which may comprise aluminum, ceramic, or a combination thereof, may alsobe resistively heated in order to achieve relatively high temperatures,such as from up to or about 100° C. to above or about 600° C., using anembedded resistive heater element.

The faceplate 217 may be pyramidal, conical, or of another similarstructure with a narrow top portion expanding to a wide bottom portion.The faceplate 217 may additionally be flat as shown and include aplurality of through-channels used to distribute process gases. Plasmagenerating gases and/or plasma excited species, depending on use of theRPS 201, may pass through a plurality of holes, shown in FIG. 2B, infaceplate 217 for a more uniform delivery into the first plasma region215.

Exemplary configurations may include having the gas inlet assembly 205open into a gas supply region 258 partitioned from the first plasmaregion 215 by faceplate 217 so that the gases/species flow through theholes in the faceplate 217 into the first plasma region 215. Structuraland operational features may be selected to prevent significant backflowof plasma from the first plasma region 215 back into the supply region258, gas inlet assembly 205, and fluid supply system 210. The faceplate217, or a conductive top portion of the chamber, and showerhead 225 areshown with an insulating ring 220 located between the features, whichallows an AC potential to be applied to the faceplate 217 relative toshowerhead 225 and/or ion suppressor 223. The insulating ring 220 may bepositioned between the faceplate 217 and the showerhead 225 and/or ionsuppressor 223 enabling a capacitively coupled plasma (CCP) to be formedin the first plasma region. A baffle (not shown) may additionally belocated in the first plasma region 215, or otherwise coupled with gasinlet assembly 205, to affect the flow of fluid into the region throughgas inlet assembly 205.

The ion suppressor 223 may comprise a plate or other geometry thatdefines a plurality of apertures throughout the structure that areconfigured to suppress the migration of ionically-charged species out ofthe first plasma region 215 while allowing uncharged neutral or radicalspecies to pass through the ion suppressor 223 into an activated gasdelivery region between the suppressor and the showerhead. Inembodiments, the ion suppressor 223 may comprise a perforated plate witha variety of aperture configurations. These uncharged species mayinclude highly reactive species that are transported with less reactivecarrier gas through the apertures. As noted above, the migration ofionic species through the holes may be reduced, and in some instancescompletely suppressed. Controlling the amount of ionic species passingthrough the ion suppressor 223 may advantageously provide increasedcontrol over the gas mixture brought into contact with the underlyingwafer substrate, which in turn may increase control of the depositionand/or etch characteristics of the gas mixture. For example, adjustmentsin the ion concentration of the gas mixture can significantly alter itsetch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc.In alternative embodiments in which deposition is performed, it can alsoshift the balance of conformal-to-flowable style depositions fordielectric materials.

The plurality of apertures in the ion suppressor 223 may be configuredto control the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 223. For example, theaspect ratio of the holes, or the hole diameter to length, and/or thegeometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 223 is reduced. The holes in the ion suppressor 223 mayinclude a tapered portion that faces the plasma excitation region 215,and a cylindrical portion that faces the showerhead 225. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 225. An adjustable electrical bias mayalso be applied to the ion suppressor 223 as an additional means tocontrol the flow of ionic species through the suppressor.

The ion suppressor 223 may function to reduce or eliminate the amount ofionically charged species traveling from the plasma generation region tothe substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.It should be noted that the complete elimination of ionically chargedspecies in the reaction region surrounding the substrate may not beperformed in embodiments. In certain instances, ionic species areintended to reach the substrate in order to perform the etch and/ordeposition process. In these instances, the ion suppressor may help tocontrol the concentration of ionic species in the reaction region at alevel that assists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasmapresent in first plasma region 215 to avoid directly exciting gases insubstrate processing region 233, while still allowing excited species totravel from chamber plasma region 215 into substrate processing region233. In this way, the chamber may be configured to prevent the plasmafrom contacting a substrate 255 being etched. This may advantageouslyprotect a variety of intricate structures and films patterned on thesubstrate, which may be damaged, dislocated, or otherwise warped ifdirectly contacted by a generated plasma. Additionally, when plasma isallowed to contact the substrate or approach the substrate level, therate at which oxide species etch may increase. Accordingly, if anexposed region of material is oxide, this material may be furtherprotected by maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240electrically coupled with the processing chamber to provide electricpower to the faceplate 217, ion suppressor 223, showerhead 225, and/orpedestal 265 to generate a plasma in the first plasma region 215 orprocessing region 233. The power supply may be configured to deliver anadjustable amount of power to the chamber depending on the processperformed. Such a configuration may allow for a tunable plasma to beused in the processes being performed. Unlike a remote plasma unit,which is often presented with on or off functionality, a tunable plasmamay be configured to deliver a specific amount of power to the plasmaregion 215. This in turn may allow development of particular plasmacharacteristics such that precursors may be dissociated in specific waysto enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 aboveshowerhead 225 or substrate processing region 233 below showerhead 225.Plasma may be present in chamber plasma region 215 to produce theradical precursors from an inflow of, for example, a fluorine-containingprecursor or other precursor. An AC voltage typically in the radiofrequency (RF) range may be applied between the conductive top portionof the processing chamber, such as faceplate 217, and showerhead 225and/or ion suppressor 223 to ignite a plasma in chamber plasma region215 during deposition. An RF power supply may generate a high RFfrequency of 13.56 MHz but may also generate other frequencies alone orin combination with the 13.56 MHz frequency.

FIG. 2B shows a detailed view 253 of the features affecting theprocessing gas distribution through faceplate 217. As shown in FIGS. 2Aand 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205intersect to define a gas supply region 258 into which process gases maybe delivered from gas inlet 205. The gases may fill the gas supplyregion 258 and flow to first plasma region 215 through apertures 259 infaceplate 217. The apertures 259 may be configured to direct flow in asubstantially unidirectional manner such that process gases may flowinto processing region 233, but may be partially or fully prevented frombackflow into the gas supply region 258 after traversing the faceplate217.

The gas distribution assemblies such as showerhead 225 for use in theprocessing chamber section 200 may be referred to as dual channelshowerheads (DCSH) and are additionally detailed in the embodimentsdescribed in FIG. 3. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 233 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 225 may comprise an upper plate 214 and a lower plate216. The plates may be coupled with one another to define a volume 218between the plates. The coupling of the plates may be so as to providefirst fluid channels 219 through the upper and lower plates, and secondfluid channels 221 through the lower plate 216. The formed channels maybe configured to provide fluid access from the volume 218 through thelower plate 216 via second fluid channels 221 alone, and the first fluidchannels 219 may be fluidly isolated from the volume 218 between theplates and the second fluid channels 221. The volume 218 may be fluidlyaccessible through a side of the gas distribution assembly 225.

FIG. 3 is a bottom view of a showerhead 325 for use with a processingchamber according to embodiments. Showerhead 325 may correspond with theshowerhead 225 shown in FIG. 2A. Through-holes 365, which show a view offirst fluid channels 219, may have a plurality of shapes andconfigurations in order to control and affect the flow of precursorsthrough the showerhead 225. Small holes 375, which show a view of secondfluid channels 221, may be distributed substantially evenly over thesurface of the showerhead, even amongst the through-holes 365, and mayhelp to provide more even mixing of the precursors as they exit theshowerhead than other configurations.

The chambers discussed previously may be used in performing exemplarymethods including etching methods. Turning to FIG. 4 is shown exemplaryoperations in a method 400 according to embodiments of the presenttechnology. Prior to the first operation of the method, a substrate maybe processed in one or more ways before being placed within a processingregion of a chamber in which method 400 may be performed. For example,features may be produced, and vias or trenches may be formed or definedwithin the substrate. The vias or trenches may have an aspect ratio, ora ratio of their height to width, greater than or about 2, greater thanor about 5, greater than or about 10, greater than or about 20, greaterthan or about 30, greater than or about 50, or more in embodiments. Insome embodiments a liner material may be formed along the trenchsidewalls to protect the substrate from metal diffusion. Additionally,an amount of cobalt may be deposited within a trench. For example, afirst portion of cobalt may be deposited within a processing chamberpositioned on a processing tool.

The chamber in which deposition is performed may be on the same tool asan etching chamber used in method 400, or in embodiments may be on adifferent tool than the chamber used in method 400. The deposition mayinclude an overhang of cobalt extending past the sidewalls of the trenchat an opening to the trench. This overhang of cobalt may constrict thetrench width at the entrance to the trench, and in embodiments, thecobalt may completely pinch off or seal the trench from furtherdeposition. Within the trench an amount of cobalt may be formed ordeposited at the bottom of the trench and along the sidewalls. Thetrench may be only partially filled in embodiments before the trenchopening is restricted or pinched off. The substrate may then betransferred to a chamber, such as chamber 200 described above, formethod 400 to be performed.

Method 400 may include flowing a precursor into a processing region of asemiconductor processing chamber at operation 405. The processing regionmay be region 233 of chamber 200 previously discussed, where thesubstrate including a portion of cobalt may be housed. The precursor maybe or include a chlorine-containing precursor in embodiments. A plasmamay be formed at operation 410 within the processing region of thechamber. The plasma may be formed from the chlorine-containing precursorto produce plasma effluents. The plasma may be formed by two electrodeswithin the processing chamber, which may include, for example, one orboth of the showerhead 255 and support pedestal 265 previouslydescribed. The plasma may be a bias plasma formed within the chamberregion that may direct plasma effluents to the substrate surface andprovide low-energy ion bombardment to the substrate.

At operation 415, an exposed region of cobalt may be contacted with theplasma effluents. The exposed region may include a portion of cobaltthat is at least partially external to a trench defined on the substratein embodiments, and may include the overhang region impinging on thetrench or sealing access to the trench. The plasma effluents may includechlorine plasma effluents, which when contacting cobalt, may modify thecobalt, and may form cobalt chloride (CoCl_(x)) at the locations ofcontact. For example, the chlorine plasma effluents may contact cobaltpreferentially outside of the trench, such as within a field region ofthe substrate, as well as cobalt within the trench. The chlorine mayalso at least initially contact cobalt external to the trench, which mayhave sealed or pinched off the entrance to the trench.

Subsequent the formation of cobalt chloride, the chlorine plasma may behalted, and the chamber may be purged with one or more inert precursorsin some embodiments. A nitrogen-containing precursor may then be flowedinto the processing region of the semiconductor processing chamber atoperation 420. The nitrogen-containing precursor may contact thesubstrate and modified cobalt at operation 425. The modified cobalt mayinclude the regions of cobalt chloride, and may interact with the cobaltchloride, while having little to no effect on unmodified regions ofcobalt. The nitrogen-containing precursor may interact with the cobaltchloride to produce volatile substances, which may then be removed fromthe chamber. The overhang portion of cobalt may have been at leastpartially converted or modified into cobalt chloride, and when contactedwith the nitrogen-containing precursor, the overhang of cobalt may be atleast partially recessed at operation 430.

The plasma formed in the processing region with the chlorine-containingprecursor may be a low-power plasma in embodiments to limit the effecton cobalt. The plasma power may be maintained relatively low to provideslight directionality to the chlorine plasma effluents. However, byusing a low power, the effluents may not extend deep into the trench.Additionally, the higher the plasma power the more likely to causesputtering at the surfaces of materials being contacted. Accordingly, bymaintaining the plasma power low, the underlying materials may remainunmodified while a surface-amount of cobalt may be modified. The plasmapower may be below or about 300 W in embodiments, depending on thethickness of the desired modification.

Higher plasma power may provide additional modification and removal ofthe overhang to form a V-shape profile at the top opening or entrance tothe trench during an operation cycle. However, a higher plasma power mayallow more material within the trench to be modified and removed, whichmay increase the number of cycles that may be used to fill the trench,and may reduce the efficiency of the method. In embodiments, the plasmapower may be below or about 250 W, below or about 200 W, below or about150 W, below or about 100 W, below or about 50 W, between about 10 W andabout 80 W, or between about 30 W and about 60 W. Utilizing a plasmapower below 100 W may afford more control on the amount of cobaltmodified at the bottom of the trench, and may allow increased control onthe modification.

The chlorine-containing precursor flowing into the processing region maybe provided in a low dose in embodiments to ensure an un-saturatedreactant, such as chlorine, in this operation. This may limit the effecton cobalt formed at the bottom of the trench. The low-dose precursorplasma may modify a surface-amount of cobalt only or the overhang ofcobalt more than cobalt formed at the bottom of the trench. By using alow-dose reactive precursor, the plasma effluents may not extend deepinto the trench during the operations. Accordingly, by maintaining thelow dose of chlorine-containing precursor flow and/or delivering thechlorine-containing precursor for a reduced time period, such as with apulsed operation, the underlying materials may remain unmodified while asurface-amount of cobalt may be modified.

The flow rate of the chlorine-containing precursor may be less than orabout 50 sccm in embodiments, and may be less than or about 45 sccm,less than or about 40 sccm, less than or about 35 sccm, less than orabout 30 sccm, less than or about 25 sccm, less than or about 20 sccm,less than or about 15 sccm, less than or about 10 sccm, less than orabout 5 sccm, or less. Additionally, the chlorine-containing precursordelivery may be pulsed for time periods of less than or about 40 secondsin embodiments, and may be pulsed for time periods of less than or about35 seconds, less than or about 30 seconds, less than or about 25seconds, less than or about 20 seconds, less than or about 15 seconds,less than or about 10 seconds, less than or about 5 seconds, or less.Additionally, the flow rate and pulsing may be combined for any of thelisted numbers. For example, the chlorine-containing precursor flow ratemay be below or about 10 sccm and may be delivered in pulses from about5 to about 10 seconds in embodiments, depending on the thickness of thedesired modification. Because only the modified regions of cobaltchloride may be subject to removal by the nitrogen-containing precursor,controlling the amount of material that is converted provides controlover the material that is removed.

Other process conditions may impact the performance of the operations aswell. A temperature within the processing chamber or at the substratelevel may be maintained between about 50° C. and about 500° C. inembodiments. The temperature may be maintained below or about 500° C. inembodiments, and may be maintained below or about 450° C., below orabout 400° C., below or about 350° C., below or about 300° C., below orabout 250° C., below or about 200° C., below or about 150° C., below orabout 100° C., or lower. The temperature may also be maintained betweenabout 100° C. and about 300° C. in embodiments, and may be maintainedbetween about 175° C. and about 250° C. during operations of the etchingmethod 400. In embodiments the temperature may be maintained within thisrange for all operations of method 400. In some embodiments thetemperature may be adjusted up or down between the two contactingoperations 415 and 425.

A higher processing temperature may allow the nitrogen-containingprecursor to remove the cobalt chloride without further excitation inembodiments. For example, contacting the cobalt chloride with theprecursor at operation 425 may be performed between about 175° C. andabout 250° C. The nitrogen-containing precursor may interact with thecobalt chloride at this temperature producing volatile materials thatmay be expelled from the chamber. Additionally, the nitrogen-containingprecursor may not interact or chemically react with unmodified portionsof cobalt. Unlike plasma precursors which may sputter or otherwise etchmaterials on the substrate, the temperature based reaction of thenitrogen-containing precursor may be limited to the modified portions ofcobalt, and may maintain the unmodified regions, including regionswithin the trench. Accordingly, in some embodiments, the processingregion of the chamber may be maintained plasma-free during operation 425of contacting the cobalt chloride with the nitrogen-containingprecursor.

A pressure within the chamber may be maintained below or about 5 Torr inembodiments. A lower pressure may provide a more anisotropic process.The pressure may be maintained below or about 4 Torr in embodiments, andmay be maintained below or about 3 Torr, below or about 2 Torr, below orabout 1 Torr, below or about 100 mTorr, or lower. In embodiments thepressure may be maintained between about 500 mTorr and about 2 Torr.

As explained previously, the modification depth may affect the degree ofcobalt removal during the etching method 400. This may also impact theamount of cobalt material removed from within the trench, where asmaller amount of modification may reduce an amount of cobalt removedfrom within the trench. The low plasma power and/or lowchlorine-containing precursor flow rate discussed previously may allowthe removal to be limited to less than or about 5 nm of cobalt duringthe operation. Additionally, the low plasma treatment and/or lowchlorine-containing precursor flow rate may provide a removal of lessthan or about 4 nm, less than or about 3 nm, less than or about 2 nm,less than or about 1 nm, less than or about 9 Å, less than or about 8 Å,less than or about 7 Å, less than or about 6 Å, less than or about 5 Å,less than or about 4 Å, less than or about 3 Å, less than or about 2 Å,or less in embodiments, down to a few molecules of cobalt. In someembodiments the removal may be at least about 5 Å, and may be betweenabout 4 Å and about 2 nm of removal, or between about 5 Å and about 1 nmof removal.

Because of the reduced amount of cobalt removal in some embodiments, theprocess may involve cycling certain operations. Optional purgeoperations may be performed after each contacting operation to reducethe interaction of the plasma effluents of the chlorine-containingprecursor and the nitrogen-containing precursor. Method 400 mayrepresent one cycle of a process for recessing or removing cobalt from asubstrate. In some embodiments, method 400 may be repeated for at leasttwo cycles, and may be repeated for at least 3 cycles, at least 4cycles, at least 5 cycles, at least 6 cycles, at least 7 cycles, atleast 8 cycles, at least 9 cycles, or more. The number of cycles may bedependent on the amount of removal provided by each cycle. For example,a total amount of cobalt may be removed in a single cycle that issufficient to provide adequate access to the trench for furtherdeposition.

In some embodiments, each cycle may remove between about 5 Å and about10 Å of cobalt, and a total amount of cobalt of a few nanometers may beperformed with additional cycles. For example, the cycling of method 400may remove at least about 10 Å of cobalt, and may remove at least about15 Å, at least about 20 Å, at least about 25 Å, at least about 30 Å, atleast about 40 Å, at least about 45 Å, at least about 50 Å, or moredepending on the amount of cobalt deposited, and the amount sought forremoval. The method may preferentially remove cobalt at the surface ofthe trench proximate the field region of the substrate. This may in partbe from the overhang of cobalt that may both pinch off access to thetrench for deposition, but may also protect cobalt within the trenchfrom etching operations. Accordingly, during multiple cycles, the firstcycle, two cycles, three cycles, or more may perform a recessexclusively on material pinching off access to the trench. Additionaletching operations may further remove this material while removing aportion of material within the trench. As the access to the trench isincreased, additional plasma effluents may access the trench and beginto modify the cobalt formed within the trench. The process may be haltedwhen cobalt within the trench has been recessed, or may be continueduntil a certain threshold of cobalt has been removed either externallyto the trench or within the trench.

The amount of cobalt that is modified and removed from within the trenchmay be less than the amount removed from the field region and from theaccess to the trench. For example, the amount of material removed fromwithin the trench may be less than or about 90% of the total materialwithin the trench or of the amount removed from the field region of thesubstrate. Additionally, the amount of material removed from within thetrench may be less than or about 85%, less than or about 80%, less thanor about 75%, less than or about 70%, less than or about 65%, less thanor about 60%, less than or about 55%, less than or about 50%, less thanor about 45%, less than or about 40%, less than or about 35%, less thanor about 30%, less than or about 25%, less than or about 20%, less thanor about 15%, less than or about 10%, less than or about 5%, less thanor about 1%, or less of the total amount within the trench, proximate abottom of the trench, or of the amount removed from the field region ofthe substrate. In some embodiments the cobalt material within the trenchor formed at a bottom of the trench may be substantially or essentiallymaintained during method 400.

The precursors used to form plasma may include a chlorine-containingprecursor, or a halogen-containing precursor in embodiments. Theprecursor may include chlorine, bromine, fluorine, or other etchantsthat may interact with the cobalt under plasma conditions. Achlorine-containing precursor may include chlorine (CL₂), or may includea diatomic precursor including chlorine or a halogen. Thenitrogen-containing precursor may include nitrogen, carbon, and/orhydrogen in any combination. For example, the nitrogen-containingprecursor may include one or more methyl moieties coupled with nitrogen,or some other carbon based moiety. Exemplary nitrogen-containingprecursors include amines, diamines, including aliphatic and aromaticdiamines, including linear aliphatic diamines, branched aliphaticdiamines, phenylenediamines, and other nitrogen-containing precursors.Exemplary precursors may include tetramethylethylenediamine (TMEDA) inembodiments. Either precursor may include additional carrier gasesincluding chemically inert precursors including helium, argon, xenon,and other noble gases or precursors that may not chemically react withcobalt.

Method 400 may optionally include deposition operations that may occuron the same tool as the etching method, or on a different tool. In someembodiments in which the deposition and etching are performed on thesame tool, a vacuum may be maintained between the operations, which mayreduce contaminants, moisture, and other handling issues. The method mayoptionally include depositing additional cobalt in the trench. Thedeposition may additionally deposit on the field region as well, and inembodiments may produce a subsequent overhang of cobalt. In someembodiments the overhang may be produced in the additional deposition bydesign, which may protect additional cobalt deposited within the trench.The etching operations of method 400 may then be repeated in asubsequent set of cycles as previously explained. Within a certainnumber of iterations of deposition and removal, the trench may be filledwith cobalt in a void-free and seam-free fill. Additional operations maybe performed in between the iterations and cycles, including reflow inembodiments.

The methods may also optionally include a hydrogen treatment betweenrecess or removal and deposition operations. Modification of thematerial to produce cobalt chloride and then removal of cobalt chloridemay produce residue on the cobalt that may cause peeling of subsequentlyformed or deposited materials. By conducting a treatment with ahydrogen-containing precursor, residue materials may be removed toensure a clean surface of the formed film. The hydrogen treatment mayinclude contacting the substrate with effluents of a hydrogen-containingplasma at optional operation 435. The plasma effluents may removeresidue from exposed cobalt surfaces at optional operation 440. Theoptional hydrogen treatment may be performed in the same chamber as theother operations of method 400 such that the entire method 400 isperformed in a single chamber, such as chamber 200 as previouslydescribed. Additionally, in some embodiments one or more operations maybe performed in a different chamber as other operations of method 400.

The hydrogen treatment may include forming the plasma effluents remotelyor at the substrate level. For example, the hydrogen-containingprecursor may be flowed into a remote plasma region, such as a remoteplasma unit, or a remote section of a processing chamber, such as region215 discussed previously with respect to chamber 200. Additionally, thehydrogen-containing precursor may be flowed into the processing regionin which the substrate is housed, and a plasma may be formed. Thehydrogen plasma effluents may interact with impurities and residuematerials and remove them from exposed cobalt surfaces within thetrench, including sidewalls and material along the bottom of the trench.Hydrogen formed by plasma processes may not interact with cobalt, andmay not affect the cobalt on which the residue may be located. In thisway, the cobalt surfaces may be cleared of residue material prior toadditional deposition material or reflow, which may maintain a highquality cobalt fill.

The plasma process performed may interact with liner or barriermaterials formed along the trench, and in embodiments may interact withmaterials within which the trenches are defined or formed. Based on thetemperature and plasma characteristics used in the operations, thepresent technology may etch cobalt selectively over liner material andother substrate materials. For example, the liner may include one ormore metals, including transition metals, as well as nitrides of metals.The metals may include, for example, titanium, titanium nitride,tantalum, tantalum nitride, ruthenium, and other materials and nitrides.The present technology may selectively etch cobalt over liner materials,such as titanium nitride, at an etch rate ratio greater than or about20:1, and in embodiments may etch cobalt at an etch ratio greater thanor about 30:1, greater than or about 40:1, greater than or about 50:1,greater than or about 60:1, greater than or about 70:1, or more inembodiments.

The present technology may also etch cobalt over silicon-containingmaterials, including silicon oxide and silicon nitride, at an etch rateratio greater than or about 50:1. In embodiments, the present technologymay etch cobalt at an etch rate ratio compared to silicon-containingmaterials greater than or about 60:1, greater than or about 70:1,greater than or about 80:1, greater than or about 90:1, greater than orabout 100:1, greater than or about 110:1, greater than or about 120:1,greater than or about 150:1, or higher.

Turning to FIGS. 5A-5D are shown cross-sectional views of substrates onwhich the present technology may be performed. FIG. 5A illustrates across-sectional view of a substrate 505 on which a trench has beenformed. A liner 510 may be formed within the trench and may produce abarrier on the sidewalls and the base. The liner may include titaniumnitride, tantalum nitride, other transition metals or transition metalnitrides, and may protect the substrate 505 from metal diffusion. Afirst amount of cobalt 515 may be formed or deposited within the trenchand on the liner material 510. When deposited, the cobalt 515 mayproduce an overhang 516, which may be a portion of cobalt that formsacross the trench opening. Although illustrated as partially coveringthe trench opening, in some embodiments the overhang 516 may completelypinch off or seal the trench, which may prevent further depositionwithin the trench.

FIG. 5B illustrates a plasma modification in which plasma effluents 520of a chlorine-containing precursor are produced. The chlorine-containingprecursor may be flowed into a substrate processing region where aplasma may be formed to produce the plasma effluents. The overhang 516and field regions above the trench may be contacted with the plasmaeffluents 520 to produce a region of modified cobalt 517. The modifiedcobalt 517 may be or include cobalt chloride. The degree to which themodified cobalt 517 extends into the trench may depend on the extent towhich the overhang 516 seals the trench, the plasma power, and theprocessing conditions. It is to be understood that FIG. 5B is an exampleillustration to show a modified surface, and is not necessarily to scaleor with an accurate amount of modification.

Subsequent the modification, a nitrogen-containing precursor may beflowed into the processing region. The nitrogen-containing precursor maycontact the modified cobalt 517 to produce volatile materials, which maybe extracted from the chamber. As illustrated in FIG. 5C, after thenitrogen-containing precursor has contacted and removed the modifiedcobalt 517, the overhand 516 may be recessed or removed, which mayprovide access to the trench. The modification and removal may beperformed multiple times in order to provide adequate access to thetrench. Additional operations may be performed, which may include reflowor a hydrogen-plasma treatment as previously discussed.

An additional amount or second amount of cobalt 525 may be deposited onthe substrate as illustrated in FIG. 5D. As shown, the second amount ofcobalt 525 may further extend the fill within the trench, such as alongthe sidewalls and/or along or proximate the bottom of the trench. Thesecond amount of cobalt 525 may be deposited to produce a secondoverhang 526 as illustrated. The second overhang 526 may also extendacross the trench opening, and may completely seal or pinch off thetrench opening, which may limit further deposition. The second overhangmay similarly be produced purposefully to protect the cobalt depositedwithin the trench from excessive removal. As explained previously, anadditional modification and removal may be performed, followed byadditional deposition, removal, and deposition if required. Inembodiments the deposition and removal may be repeated at least twicebefore a final deposition may fill the trench. By performing themodification and removal as explained throughout the disclosure, thepresent technology may provide a greater cobalt fill, and reduce cobaltremoval from within the feature during the etching operations. This mayreduce queue times for filling trenches, and may provide an improvedquality of cobalt fill that may not suffer from peeling of additional orsubsequent layers of material.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology. Additionally, methods orprocesses may be described as sequential or in steps, but it is to beunderstood that the operations may be performed concurrently, or indifferent orders than listed.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a precursor” includes aplurality of such precursors, and reference to “the layer” includesreference to one or more layers and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

1. An etching method comprising: flowing a chlorine-containing precursorinto a processing region of a semiconductor processing chamber; forminga plasma of the chlorine-containing precursor to produce plasmaeffluents; contacting an exposed region of cobalt with the plasmaeffluents, wherein the plasma effluents produce cobalt chloride at theexposed region of cobalt; flowing a nitrogen-containing precursor intothe processing region of the semiconductor processing chamber;contacting the cobalt chloride with the nitrogen-containing precursor;and recessing the exposed region of cobalt.
 2. The etching method ofclaim 1, wherein a plasma power of the plasma formed from thechlorine-containing precursor is less than about 100 W.
 3. The etchingmethod of claim 1, wherein a temperature of the substrate is maintainedbetween about 175° C. and about 250° C. during the etching method. 4.The etching method of claim 1, wherein a pressure within thesemiconductor processing chamber is maintained below about 5 Torr. 5.The etching method of claim 1, wherein the etching method removes atleast about 5 Å of cobalt.
 6. The etching method of claim 1, furthercomprising depositing additional cobalt in the trench, and producing anoverhang of cobalt.
 7. The etching method of claim 1, wherein theetching method is repeated for at least two cycles.
 8. The etchingmethod of claim 7, wherein a total removal of cobalt after the at least2 cycles is at least about 20 Å.
 9. The etching method of claim 1,further comprising, subsequent to recessing the exposed region ofcobalt, contacting the substrate with effluents of a hydrogen-containingplasma, and removing residue from exposed cobalt surfaces.
 10. Theetching method of claim 1, wherein the method removes less than 5% ofmaterial proximate a bottom region of the trench.
 11. The etching methodof claim 1, wherein the etching method has a selectivity of cobalt totitanium nitride greater than or about 50:1.
 12. The etching method ofclaim 1, wherein the etching method has a selectivity of cobalt tosilicon nitride and silicon oxide greater than or about 100:1:1.
 13. Theetching method of claim 1, wherein the processing region is maintainedplasma-free while contacting the cobalt chloride with thenitrogen-containing precursor.
 14. A method of producing a gap-freecobalt fill, the method comprising: depositing a first amount of cobaltinto a trench defined on a substrate; flowing a chlorine-containingprecursor into a processing region of a semiconductor processingchamber, wherein the processing region houses the substrate; forming aplasma of the chlorine-containing precursor to produce plasma effluents;contacting a region of the cobalt proximate an entrance to the trenchwith the plasma effluents to produce cobalt chloride; flowing anitrogen-containing precursor into the processing region of thesemiconductor processing chamber; contacting the cobalt chloride withthe nitrogen-containing precursor; and recessing the cobalt.
 15. Themethod of producing a gap-free cobalt fill of claim 14, furthercomprising depositing a second amount of cobalt into the trench, whereinthe deposition forms an overhang of cobalt at the opening of the trench.16. The method of producing a gap-free cobalt fill of claim 14, whereinthe method is repeated at least twice.
 17. The method of producing agap-free cobalt fill of claim 14, wherein the cobalt is at least 80%maintained in the trench while recessing the cobalt proximate theentrance to the trench.
 18. The method of producing a gap-free cobaltfill of claim 14, wherein a plasma power of the plasma formed from thechlorine-containing precursor is less than or about 60 W, wherein theflow rate of the chlorine-containing precursor is below or about 30sccm, and wherein the chlorine-containing precursor is flowed into theprocessing region for a time period of less than or about 20 seconds.19. The method of producing a gap-free cobalt fill of claim 14, furthercomprising, subsequent to recessing the cobalt, contacting the substratewith effluents of a hydrogen-containing plasma, and removing residuefrom exposed cobalt surfaces.
 20. The method of producing a gap-freecobalt fill of claim 14, wherein the cobalt is deposited on a metallicnitride liner formed within the trench.